“Feisty? My least favourite word. Have you ever heard a man described as Feisty,” she said in an interview with the Mail on Sunday’s You magazine.

“Have you heard a male character described as feisty? I think not.”

But she accepts that her character is unconventional by the standards of the day.

“She’s so desperate for things to change and to be heard that occasionally she’ll speak her mind, and that sometimes upsets people,” said Lewis, 29, who lives in Dalston, east London.

“You can’t play a character unless you believe what they believe. I can relate to her personally – she is fighting for equality across the board – but what’s interesting is that lots of people think she is a troublemaker.”

However Lewis’ own history is firmly rooted in the British establishment.

Her father John Lewis is chairman of London’s Groucho Club and part owns the Sloane Square hotel. He also transformed Cliveden from notorious stately home to luxury hotel.

Her great-great uncle was the artist John Merton, whose sitters included the Queen and Princess Diana.

She attended Port Regis preparatory school and then Bryanston, which she left before completing her GCSEs after being bullied. She studied literature at King’s College and until landing the role in Downton tutored students in Latin Greek and English.

Lewis, is expected to become the love interest of Lady Sybil’s widower Tom Branson in the next series.

But she claims she rarely has time for romance.

“It’s hard to be able to be with somebody and make a commitment to them when your first love is your work,” she said. “It’s a special person who will put up with that.”